Grinding machine



March 10, 1942. F. TURRETTINI 2,276,260

` GRINDING MACHINE Filed June 30, 1939 2 Sheets-Sheet l March 1o, i942.

F. TURRETTINI 2,276,260

GRINDING MACHINE Filed June 30, 1959 -2 Sheelzs-Sheei'I 2 Patented Mar. 10, 1942 UNITED STATES .TNT OFFICE GRINDING MAOHNE ofl Switzerland Application June 30, 1939, Serial No. 282,275 In Switzerland July 18, 1938 3 Claims.

The present invention relates to grinding machines and in particular to machines for grinding the threads of a workpiece as thread cutting tools and the like.

Certain types of grinding machines provide two cams, one of which is adapted to exert an effect upon the profile of the workpiece, which appears in the section through the axis of rotation of the workpiece, and the other cam is adapted to exert an eiect upon the profile appearing in a perpendicular section relative to said axis of the workpiece, each cam acting upon the organ which regulates the distance between the axis of the grinding wheel and the axis of the workpiece by the intermediary of a slidable piece.

The object of the invention is, on the one hand the provision, of two reduction devices, each of which is constituted by an inclined plane member of micrometrically adjustable inclination and associated to one of said cams, and on the other hand, the provision of a-hinged roller system,

which is operable by means of said slidable piece for rolling on` said plane members and bearing against said organ which regulates the distance between the two axes of the grinding wheel and the workpiece', respectively, so as to move this organ when the hinged roller system rolls on the inclined plane members.

The invention consists furthermore in the construction and arrangement of certain parts as will be apparent from the following description and claims, reference being had to the accompanying drawings which show one embodiment of the present invention.

In the drawings:

Figure l is a plan view of the embodiment, A

partly drawn in section, illustrating a screw thread grinding machine according to the invention.

Figure 2 is a lateral elevation thereof, partly A thereby moved under the action of a servomotor 3l. The table Iii-carries aspindle=head.9 providing the rotatable center, and a tailstock I1 providing the back center 8a, between which centers the workpiece 20 is mounted for rotation. On the axle of the back center 8a is arranged an adjustable truing tool 40 for truing the prole of the grinding wheel 2I. This tool may-be a diamond for instance, or an abrading point of harder material than that of the grinding wheel. The drive shaft I is mounted in bearings integral with the machine bed and can be operated by a not represented motor, by the intermediary of the pulley 2. The rotation of this shaft I is transmitted upon the spindle 8 in the spindle head 9 by means of a chain I0 driven by a sprocket wheel slidably keyed on the shaft I. By means of gear Wheels Il and I2 the spindle 8 is connected to the lead screw I3 journalled in the table I6 and turning in a nut I4 which is secured to themachine bed I5, whereby the ratio of said gear wheels can be adapted to the desired pitch of the thread of the workpiece 20. The shaft I drives furthermore, by the intermediary of the gear wheels 4, 5, 6 and 1, a shaft 3 carrying two cams I8 and I9 and rotating with the same speed as the spindle 8.

The cam I8 is provided for generating the profile of the workpiece, which would clearly appear in a section along the geometric axis of the workpiece, that is to say the screw thread profile,

n while the cam I9 is provided for generating a profile in a plane perpendicular to the axis of the workpiece, which can be the concentric prole of an ordinary screw, for instance, or the relieved prole of a screw tap.

The device connecting one or the other of cams I8v and I9 in operative relation with the servomotor 3| comprises an axially slidable rod 91 carrying two rollers 98 and 99 disposed on the same side of the rod and being adapted to be put into contact with the corresponding cam,.either the first roller 98 with the cam I8 or the second roller 99 with the camv I9. Two plane members |01 and |08 following each other in the direc,-

tion of axial displacement of the rod' 9`I have their plane surfaces vertically arranged and adjustably inclined with respect to said axial direction of the rod. A vertical support vI Ill'being integral with the machine bed separates the two members and forms a certain alignment with their plane surfaces. The ends of the two lmembers, which are adjacent to this support, are rotatably mounted in III and II2, respectively, on the machine bed, whereas theV other free ends abut eachy against the end of amicrometerv screw |09., respectivelyA Ill Il; Thesev twov screwsfr permit the accurate adjustment of the inclinations of the plane members. Opposite to these members is disposed a plate I I3 which is integral with the rod 32 forming the leading organ of the servomotor. The latter receives the necessary force for moving the table 33 from pressure fluid arriving through a pipe 35 and leaving by pipe 36. The rod 91 carries at the right end a hinged parallelogram |I which in turn carries two rollers |02 and |03. When the rod 91 reciprocates, this parallelogram is moved in the passage formed by the inclined member |01 or |08 and the plate I3, whereby the roller |02 co-operates with the Plane surface of a member, while the roller |03 co-operates with the surface of the plate.

Finally, the rod S'I carries two fixed collars I04 and |05, spaced from each other, and therebetween two discs |06 and I I9 slidable on the rod and adapted to abut against the collars. A coil spring |20 is disposed between the two discs and all three parts are located in a casing |00 which can be displaced along guideways by means of the handle |008.. The two ends of the casing penetrated by the rod give free passage for the collars, but stop the slidable discs which can abut against said ends.

In the position shown in the drawings the spring |20 bears, on the one hand, by the intermediary of the disc I I9, against the right end of the stationary casing |00 and, on theother hand, by the intermediary of the disc |06 against the collar |04, so that the roller 99 is continually applied against the cam I 9. Under the action of the rotating cam I9 the hinged system I0| is displaced along the inclined plane member |01 wherethrough the plate I I3 is subjected to a displacement which is perpendicular to that one of the rod S'I, and which produces by the intermediary of the servo-motor 3| a corresponding displacement of the table 33. There is an intermediate position of the rod 91 wherein none of the rollers 98 and 99 registers with its cam; inw

this case the spring |20 which is initially tensioned, expands between the two collars |04 and |05. If the casing |00 is then shifted to the right, the spring |20 bears with the disc |06 against the left side of the casing and with the disc ||9 against the collar |05 and applies the roller 98 against the cam I8. At the same time the hinged system IOI co-operates by means of the roller |02 with the'Dlane surface of the inclined member |08.

The performance of the machine is the following: The table I6 is moved in order to bring the truing tool 40 into opposition with the grinding wheel 2|. Then the servo-motor 3| is submitted to the action of the cam I8 and the pulley 2 is thrown into gear. The spindle 8 and the workpiece 20 begin to rotate while the table I6 moves over a determined length according to the ratio of the gear wheels and I2. The table 33, and the grinding wheel therewith, moves in the guideways 339. under the action of the servo-motor 3| which is operated by the cam I8. By this truing procedure the grinding wheel 21| is provided with the exact profile. Afterwards the pulley 2 is disengaged, the table is moved so that the workpiece 20 comes opposite the grinding wheel 2|, and the servo-motor is submitted to the action of the cam I9. When the pulley 2 is re-engaged, the accurately trued grinding wheel 2| generates the desired prole on the workpiece While the reciprocating motion imparted to the carriage of the grinding wheel produces the relieving of the threads if the workpiece is a tool as a screw tap or a thread milling cutter. For grinding screw threads without the relieving the action of the servo-motor 3| is stopped by shifting the spring casing |00 into half-way position so that none of the rollers 98 and 99 registers with the corresponding cam.

The advantages of the above described machine are evident.

For generating a Whitworth thread of eleven threads per inch, for instance, the unique cam type for the Whitworth system is mounted on the shaft 3 of the machine, from which cam all the various Whitworth thread profiles can be derived, and the inclination of the plane member working in connection with this cam is adjusted in such a manner that the distance between the axes of the grinding wheel and the workpiece, respectively, is varied during one revolution of the latter for an amount which exactly corresponds with the depth of the Whitworth thread of eleven threads per inch.

As the lead screw I3 of the table I0 is connected with the spindle 8 entraining the workpiece 20, by means of the exchangeable reduction gear II and I2 which determines the pitch to be produced on the workpiece, the simultaneous effect of the axial displacement of the workpiece under the action of the lead screw, and of the perpendicular movement of the grinding wheel under the action of the cam and the variable reduction device will generate the desired thread profile which, at first, can be reproduced on the grinding wheel 2| by means of the truing tool 130, and then on the workpiece 20 by means of the trued grinding wheel.

If a metric thread (International system) with a pitch of two millimeters, for instance, is concerned, the procedure is exactly the same as above: The unique cam type for the International system is mounted on the machine and the variable reduction device is adjusted in order to generate the depth of the thread of a two millimeter pitch.

The second cam acts upon the radial section of the workpiece, that is to say, it is used to generate the relieving of the threads of screw taps or thread milling cutters. The number of the flutes of the tap are determined by the number of recesses on the drive of this second cam and the depth of the relieving is determined by the adjustment of the variable reduction device acting in connection with this cam.

The number of cams which are necessary for giving the predetermined thread to a workpiece is thus limited to a minimum, because all the treads of different pitches of a same thread systern are obtained, with respect to their proles appearing in an axial section, by a single cam type and all the depths of the relieving corresponding to a determined number of iiutes of a tap are obtained by a single cam type having the same number of recesses. Finally, the fact that there is a variable reduction device for each cam facilitates the passage from one cam to the other and avoids that they are put out'of adjustment during the performance of the truing or the relieving work.

In the modification of Fig. 3 the rod 91 is hingedly connected by the piece ||8 to a frame II5 which is slidable in two bearings IIB and II'I I claim: 1. In a grinding machine, in combination a machine bed, displaceable means on said bed for supporting and rotating the Work piece, a grinding Wheel rotatably mounted on said machine bed, means for reciprocating either the Work piece or grinding Wheel in a transverse movement perpendicular to the axis of rotation of the other not reciprocated part, a reciprocatable organ controlling the said transverse movement, an adjustable Wheel profiling tool mounted for displacement with the Work piece, a rotatable cam system comprising two dii-ferent cams, two reduction devices each one being constituted by an inclined plane member of micrometrcally adjustable inclination, a slidable rod adapted to cooperate alternatively with one and the other of said cams, and a hinged roller system on said rod adapted to bear on said inclined plane members on one side and against said reciprocatable organ on the other side, said cams being alternatively adapted to reciprocate said organ by the intermediary of said rod and hinged roller system so as to accomplish the dual function of, rst generating by means of said proling tool the prole of the grinding Wheel in a section along the axis of the Work piece and, second generating by means of said Wheel the prole of the Work piece in a section perpendicular to the axis of said piece.

2. In a grinding machine, in combination a machine bed, displaceable means on said bed for supporting and rotating the work piece, a grinding wheel rotatably mounted on said machine bed, a servo-motor having a reciprocatable organ for reciprocating said grinding Wheel in a transverse movement perpendicular to the axis of rotation of the Work piece, an adjustabler Wheel profiling tool mounted for axial displacement with the Work piece, a rotatable cam system comprising `two diierent cams on a common axle, means for imparting rotation to the Work piece and cams and effecting axial displacement of work piece and profiling tool, means for varying the rate of said displacement, two reduction devices, each one being constituted by an inclined plane member of micrometrically adjustable inclination, a rod carrying tWo rollers adapted to cooperate each with one of said cams, said rod being capable of sliding movement to and fro for bringing each of said rollers alternatively into contact with the cooperating cam, and a frame connected to said rod and carrying a hinged roller system adapted to bear on one or the other of said inclined plane members on one side and against said reciprocatable organ on the other side, said cams being alternatively adapted to reciprocate said organ by the intermediary of said rod, frame and hinged roller system, when said roller system bears on said inclined plane members, so as to accomplish the dual function of, rst generating by means of said proling tool the profile of the grinding Wheel in a section along the axis of the work piece and, second generating by means of said Wheel the profile of the Work piece in a section perpendicular to the axis of said piece.

3. Grinding machine according to claim 2 for generating the relieved threads of thread cutting tools, one of said cams being so constructed as to reproduce on the grinding Wheel, by means of the profiling tool and in cooperation with one of the rollers on said slidable rod, one of said adjustable reduction devices and the reciprocatable organ of said servo-motor the longitudinal profiles of al1 thread sizes of a same thread system, and the other of said cams being provided with recesses so as to generate the profile on the Work piece, by means of said grinding wheel and, simultaneously in cooperation with the other roller on said slidable rod, the other reduction device and the reciprocatable organ of said servo-motor the relieving of the threads, the number of flutes being determined by the'number of recesses on said other cam and the depths of the relieving obtained by the adjustment of the said other reduction device acting in connection with said cam.

FERNAND TURRETTIN'I. 

